<!DOCTYPE html>
<html>
   <head>
      <script type = "text/javascript" src = "https://d3js.org/d3.v4.min.js"></script>
      <style> 
        .line {
            fill: none;
            stroke: green;
            stroke-width: 5px;
         }
      </style>
   </head>
   <body>
      <script>
         // set the dimensions and margins of the graph
         var margin = {top: 20, right: 20, bottom: 30, left: 50},
         width = 960 - margin.left - margin.right,
         height = 500 - margin.top - margin.bottom;
         // set the ranges
         var x = d3.scaleTime().range([0, width]);
         var y = d3.scaleLinear().range([height, 0]);
         // define the line
         var valueline = d3.line()
            .x(function(d) { return x(d.year); })
            .y(function(d) { return y(d.population); });
         // append the svg obgect to the body of the page
         // appends a 'group' element to 'svg'
         // moves the 'group' element to the top left margin
         var svg = d3.select("body").append("svg")
            .attr("width", width + margin.left + margin.right)
            .attr("height", height + margin.top + margin.bottom)
            .append("g").attr("transform",
               "translate(" + margin.left + "," + margin.top + ")");
         // Get the data
         d3.csv("data.csv", function(error, data) {
            if (error) throw error;
            // format the data
            data.forEach(function(d) {
               d.year = d.year;
               d.population = +d.population;
            });
            // Scale the range of the data
            x.domain(d3.extent(data, function(d) { return d.year; }));
            y.domain([0, d3.max(data, function(d) { return d.population; })]);
            // Add the valueline path.
            svg.append("path")
               .data([data])
               .attr("class", "line")
               .attr("d", valueline);
            // Add the X Axis
            svg.append("g")
               .attr("transform", "translate(0," + height + ")")
               .call(d3.axisBottom(x));
            // Add the Y Axis
            svg.append("g")
               .call(d3.axisLeft(y));
         });
      </script>
   </body>
</html>